Winetech Technical Yearbook 2022

AUGUST

MULCHING ON BERMS

BY HANNO VAN SCHALKWYK

THE USE OF COVER CROPS ON BERMS is notably applied in the drier vineyard regions, like Agter-Paarl, Swartland and Darling. The advantages thereof have been well researched, with Archer and Saayman (2018) emphasising that it is particularly beneficial for the development of fine roots in the shallower soil layers (photo 1), as well as deep roots. In contrast, mechanical clean cultivation and growing weeds (or permanent cover crop) impeded the development of the vine’s interception roots in the shallower soil layers. The detrimental effects were only observed later in diminished shoot growth and subsequent lower yield. Fourie (2021) found in the Coastal Region that a mulch that was formed by mulching in the work row, decreased the irrigation requirement of a vineyard by up to 50 mm. In these cases the cover crop was terminated before bud break. Mulching improves the soil organic carbon content over time (Fourie, 2021), and according to Saayman (2016), natural

PHOTO 1. In this vineyard the interception roots developed very well in the shallower soil layers under a straw mulch.

nitrogen supply should be sufficient to meet the vines’ need on soils with higher carbon contents (≥0.7% for light and ≥0.9% for heavier texture soils). It is a very good approach to vine nutrition in drier areas where rainfall can be unpredictable and the application of conventional fertilisers therefore very difficult. Fertilisers that lie on the soil for a long time, volitalise and the

PHOTO 2. The hay on this vineyard’s berm promotes root development, and suppresses evaporation losses and summer weeds.

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WINETECH TECHNICAL YEARBOOK 2022